TempoLux™ Illumination Sensor for Human-Centric Shading and Lighting Automation

The New “Killer” Benefit of Shading and Lighting Automation: Enhanced Health and Wellness

Traditionally, window-shading and lighting automation technologies have been aimed mostly at enhancing convenience and saving energy.  However, there is a growing body of research that points to another, far more compelling, benefit: enhanced health and wellness.

The research shows that exposure to indoor illumination optimized purely for energy efficiency presents risks to human health.  The reason is that the spectral composition of high-efficiency artificial illumination differs significantly from that of daylight—and humans have become evolutionarily adapted to daylight over millions of years.

Differences in two spectral bands appear responsible for most of the health risks due to artificial illumination: the circadian band and the Near InfraRed (NIR) band:

• The circadian band is a range of wavelengths from about 430 to 490 nm which strongly influences the human circadian rhythm. Not enough circadian band irradiance during daytime—or too much circadian band irradiance at nighttime—can disrupt a healthy circadian rhythm, causing sleep disorders and a range of health issues. Unfortunately, conventional high-efficiency artificial illumination often commits both of these sins.
• The NIR band is an invisible range of wavelengths from about 780 to 980 nm which modulates important biologic processes, and which is virtually absent from high-efficiency artificial illumination.

The following chart shows high typical high-efficiency artificial illumination and daylight admitted by a window differ in these critical spectral bands:

The health risks due to these differences can be avoided by spending plenty of time outdoors during daytime and avoiding conventional high-efficiency artificial illumination at nighttime, but that’s not always convenient or even possible.

Fortunately, technology offers another way to mitigate the risks: new “circadian smart” lamps can be adjusted to emit just the right amount of circadian power for the time of day, and automated window shading can maximize healthy glare-free daylight (thereby providing both circadian reinforcement and NIR exposure).

This health-and-wellness benefit could substantially boost the market penetration of automated shading and lighting.

However, there’s still something missing: a cost-effective way of sensing illumination quality to drive the automation.

The Sensing Challenge

Sensing the health-and-wellness aspects of illumination entails sensing the irradiances in the relevant spectral bands which actually reach the people in the illuminated area.

There are two basic approaches to achieve this: the irradiances can be directly sensed with an in-situ sensor which is co-located with the people, or the in-situ irradiances can be estimated based on the output of a remote sensor  which can optionally be co-located with the shading or lighting systems.

In-situ sensing with a medical-grade spectroradiometer is the gold standard but is cost-prohibitive for mainstream use.  Less expensive wearable spectral dosimeters are emerging, but regularly using them requires a commitment that even health-conscious people might be unwilling to make.  Such a device could also be positioned in a fixed in-situ location (instead of being worn by a person), but would then be obtrusive and vulnerable to shadowing.  Today’s Personal Electronic Devices (PEDs) are capable of in-situ illuminance sensing, but lack the spectral resolution necessary to selectively sense irradiances in the key spectral bands.

On the other hand, a remote sensor is easy to integrate in a shading or lighting product (streamlining distribution and installation, can serve multiple people in the illuminated area, and doesn’t require people to carry or wear a specialized electronic device.  However, because it doesn’t directly sense the in-situ irradiances, a conventional remote sensor requires installation-specific calibration with a spectroradiometer in order to accurately estimate the in-situ irradiances in individual spectral bands.  Also, because its outputs are area-specific and not person-specific, it can’t directly produce individualized illumination-quality information.

Our TempoLux™ Illumination-Sensing Approach

Our TempoLux™ technology enables an inexpensive remote sensor (which can be readily integrated into a shading or lighting product) to estimate in-situ irradiances with sufficient accuracy without need for a specialized calibration equipment—and while still enabling users to track individualized illumination-quality metrics.

Our solution includes five components (not all of which are required in each application):

• an inexpensive three or four-channel multi-spectral sensor,
• an innovative calibration process that leverages the ambient light sensor in any PED,
• an innovative automation protocol that provides various health-oriented shading control modes,
• a power-efficient communications protocol that provides illumination-quality information to nearby PEDs without need to establish one-to-one connections, and
• an innovative algorithm to generate individualized, actionable illumination-quality metrics.

Leverages Inexpensive Multi-Spectral Sensor Technology Developed for Smartphone Cameras

Medical-grade photobiological characterization of illumination requires a precisely-calibrated high-resolution multi-spectral sensor. However, such a sensor is overkill for human-centric automation, or for providing useful health-and-wellness insights—and far too expensive for mainstream use.

Instead, TempoLux™ leverages commodity multi-spectral sensing chips developed for smartphone camera applications, coupled with an innovative calibration process that provides sufficient accuracy for mainstream health-and-wellness applications. The same chips can also do double-duty by implementing our multi-spectral glare-sensing technology for responsive glare control.

Two chips are required for TempoLux™ sensing with current sensor technology, but sensor manufacturers’ road-maps suggest that a single-chip solution will be possible soon. Here’s a block diagram of the two-chip configuration used in our current design:

Calibration Process Leverages the Ambient Light Sensor Integrated in Every PED

Our TempoLux™ calibration approach is based on four observations:

• a useful health-and-wellness-oriented illumination sensor does not require medical-grade accuracy;
• the required accuracy is further reduced because useful health-and-wellness insights can be obtained from spectral balance measurements (i.e. ratio of irradiances in at least two spectral bands) without relying on absolute in-situ irradiances;
• the typical indoor surfaces in residential and commercial spaces have reasonably flat reflectance from near-UV to near-IR wavelengths; and
• virtually every mainstream user will have access to a PED with an integrated Ambient Light Sensor (ALS) and a Bluetooth interface.

Our approach calibrates the output of the TempoLux™ 555 nm irradiance channel against the illuminance (lux) measurement provided by the PED, and then generates a calibration matrix for the other remote irradiance channels based on that single-point 555 nm calibration. The calibration process is automated, and if the shading and lighting systems are Matter-compatible, a separate calibration matrix is optionally generated for several lighting and shading settings to maximize accuracy. This approach eliminates the need for a calibration spectroradiometer, is quick and convenient, and provides sufficient accuracy for the application.

Innovative Automation Modes

When used for shading and/or lighting automation, TempoLux™ provides several control modes tailored to users’ specific needs, including:

• a daylighting mode (which adjusts the shading to maximize glare-free natural illumination);
• a circadian-optimized mode (in which the shading and/or lighting systems are controlled to provide the optimum circadian irradiance profile for a user’s wake-sleep schedule); and
• an NIR-dosing mode (in which a relatively high daylight set-point is used for shading control to maximum NIR exposure over a relatively short interval while still limiting UVA and harmful blue irradiances to safe levels).

Note that our IP covers only the shading-related aspects of these automation modes; human-centric lighting automation is covered by patents assigned to other entities.

Power-Efficient Broadcast Protocol for Illumination-Quality Information

TempoLux™ uses Bluetooth Low Energy (BLE) 5.0 extended advertising packets to broadcast sensor information to nearby PEDs without need to establish one-to-one connections—and with sufficiently low power consumption to enable photovoltaically-powered operation.

The broadcast packets also include BLE Received Signal Strength Indicator (RSSI) threshold values to enable a receiving PED to (1) determine if it is close enough for the sensor calibration to be valid, and (2) to adjust the sensor information based on RSSI for the PED’s actual location relative to the TempoLux™ sensor.

Using a broadcast protocol to convey information to PEDs also eliminates the need for the TempoLux™ sensor to have access to a user’s personal information. In effect, TempoLux™ acts as an illumination quality beacon for nearby PEDs; while they need our app to fully exploit the illumination quality information, they don’t need to pair (or have a user account) with the sensor.

Innovative Algorithm for Generation of Personalized Illumination-Quality Metrics

TempoLux™ also includes a PED-hosted algorithm that can comprehend a user’s wake-sleep schedule to generate individualized circadian-health metrics based on the broadcast sensor information. The algorithm first checks to see if the PED has a user-set wake-sleep schedule (or, in the case of a smartwatch, if a wake-sleep schedule can be inferred from existing biometric data); if not, it prompts the user to set-up a wake-sleep schedule, and then generates personalized metrics based on the sensor outputs. The algorithm is also capable of accounting for time spent outdoors if the PED’s ambient-light sensor is exposed.

Complementary Technologies

While TempoLux™ provides a highly cost-effective means of sensing key health-and-wellness aspects of illumination, it’s even more advantageous when combined with four of our other innovations:

• Our multi-spectral daylight sensing technology senses incipient daylight glare far more cost-effectively than conventional approaches, facilitating responsive daylight control. The technology uses a subset of the TempoLux™ hardware, so the glare-sensing capability is “free”.
• Our fluctuation-mitigation technology enables a responsive daylight-control system to respond quickly to isolated changes in the daylight level while ignoring sustained high-amplitude fluctuations due to moving clouds.
• Our closed-loop daylight-control algorithm for horizontal venetian blinds mitigates spurious daylight components which would otherwise confuse the output of a closed-loop sensor like TempoLux™.
• When integrated into a device that is mounted near or on a window, our multi-spectral sensor technology  works synergistically with our patented thermal-gradient sensing technology to enable minimization of HVAC energy consumption as well as high-performance daylighting and human-centric shading/lighting automation.

See our IntelliBlind™ reference design for an example of how all of these technologies can be advantageously leveraged in a single product.

Applications

Our TempoLux™ technology can be cost-effectively integrated into any remote sensor that has a clear field-of-view to an illuminated area. For example, our IntelliBlind™ Smart Miniblind Actuator and IntelliLux™ Smart Headrail Sensor incorporate TempoLux™ sensor technology. In addition to sensors for automated shading and lighting control, advantageous applications include PIR occupancy sensors and even smart thermostats.

Our TempoLux™ algorithm for generating personalized circadian-health information based on a wake-sleep schedule can also be used independently with a conventional in-situ multi-spectral sensor.